In conventional overhead-valve internal combustion engines, at least two valves reciprocate to provide intermittent communication between intake and exhaust manifolds and a combustion chamber. The valves include valve stems commonly disposed in valve stem guides supporting axial motion of the valves in an engine component such as an engine head. Lubrication is provided to upper portions of the valve stems by a spray of lubricating oil within a valve cover disposed over the engine head or by gravity flow from an associated rocker arm. Oil flows by the force of gravity and may be encouraged by a pressure differential between the manifold and crankcase along a free upper end of the valve stem toward the manifolds and valve heads.
Valve guide seals located between the valve stem and the valve guide serve various purposes. First, they minimize engine oil consumption by restricting oil entry into the manifold and the combustion chamber. Second, they help to minimize exhaust particulates that contribute to pollution. Third, they are helpful in minimizing guide wear, which is of particular importance with diesel engines due to the nature of their operation.
However, current valve seals do not account for valve guide height tolerances. If a valve guide height exceeds the specified tolerance for the associated valve seal, the seal may be deformed. Thus, the sealing of the valve stem and valve guide is compromised. Deformation of the valve seal typically occurs when the height of the valve guide is out of tolerance. Due to the increased height, the valve guide seal is compressed between a retainer and the valve guide.
Therefore, it is desirable to provide a valve seal that allows for various tolerance valve guides. Further, it is desirable that the valve seal not interfere with the action of the valve stem. It is further desirable that a single valve stem seal may be used for a variety of valve guides having multiple heights, thus allowing for the use of the same valve seal in multiple components.